Algae polysaccharide-induced transport transformation of nanoplastics in seawater-saturated porous media.

This study examined the distinct effects of algae polysaccharides (AP), namely sodium alginate (SA), fucoidan (FU), and laminarin (LA), on the aggregation of nanoplastics (NP) in seawater, as well as their subsequent transport in seawater-saturated sea sand. The pristine 50 nm NP tended to form large aggregates, with an average size of approximately 934.5 ± 11 nm. Recovery of NP from the effluent (Meff) was low, at only 18.2 %, and a ripening effect was observed in the breakthrough curve (BTC). Upon the addition of SA, which contains carboxyl groups, the zeta (ζ)-potential of the NP increased by 2.8 mV. This modest enhancement of electrostatic interaction with NP colloids led to a reduction in the aggregation size of NP to 598.0 ± 27 nm and effectively mitigated the ripening effect observed in the BTC. Furthermore, SA's adherence to the sand surface and the resulting increase in electrostatic repulsion, caused a rise in Meff to 27.5 %. In contrast, the introduction of FU, which contains sulfate ester groups, resulted in a surge in ζ-potential of the NP to -27.7 ± 0.76 mV. The intensified electrostatic repulsion between NP and between NP and sand greatly increased Meff to 45.6 %. Unlike the effects of SA and FU, the addition of LA, a neutral compound, caused a near disappearance of ζ-potential of NP (-3.25 ± 0.68 mV). This change enhanced the steric hindrance effect, resulting in complete stabilization of particles and a blocking effect in the BTC of NP. Quantum chemical simulations supported the significant changes in the electrostatic potential of NP colloids induced by SA, FU and LA. In summary, the presence of AP can induce variability in the mobility of NP in seawater-saturated porous media, depending on the nature of the weak, strong, or non-electrostatic interactions between colloids, which are influenced by the structure and functionalization of the polysaccharides themselves. These findings provide valuable insights into the complex and variable behavior of NP transport in the marine environment.

Characteristics of zero-valent iron surface oxide films under the catalytic interface reactions by assisting ligands in nitrate-contaminated groundwater.

The surface passivation layer coating on zero-valent iron (ZVI) particles impedes the electron transfer from ZVI to nitrate. To enhance the efficiency of nitrate reduction by Fe(0), we tested the chemical process and the thickness of the iron oxide film on the surface of Fe(0) particles, utilizing Fe2+aq in aqueous solution and wheat straw as ligands. A novel principal surface catalyzing reaction was formulated as follows: [Formula: see text] . When Fe2+aq concentration increased from 0 - 200 mg·L-1, the NO3- removal rate increased from 6.95% to 82.6% respectively during 12 h and it was 48%, 72%, 79% and 94% respectively in Fe0/WS ratio of 0, 0.25, 0.5 and 1 system. Uniform surface iron oxide films formed around the Fe(0) particles within 12 h after the adding Fe2+aq or wheat straw to the Fe(0) system. The composition and thickness of these films were dependent on the quantity of added materials. X-ray diffraction (XRD) analysis revealed that surface oxide iron mainly consisted of Fe2+ or Fe3+ oxides, with Fe3O4 being predominant. The X-ray photoelectron spectroscopy (XPS) etching indicated that the addition of Fe(0)/straw at mass ratios of 1 or system with 20 mg·L-1 Fe2+aq resulted in the thinnest surface iron oxide layer. The study demonstrated that reducing the oxide layer's thickness was achieved through partial catalysis and enhanced complexation capacity. This reduction was facilitated by the introduction of Fe2+aq or wheat straw into the Fe(0) system, potentially improving proton dissociation and promoting the ligand-assisted dissolution of Fe3+ oxides.

Exploring the landscape of symbiotic diversity and distribution in unicellular ciliated protists.

BACKGROUND: The eukaryotic-bacterial symbiotic system plays an important role in various physiological, developmental, and evolutionary processes. However, our current understanding is largely limited to multicellular eukaryotes without adequate consideration of diverse unicellular protists, including ciliates. RESULTS: To investigate the bacterial profiles associated with unicellular organisms, we collected 246 ciliate samples spanning the entire Ciliophora phylum and conducted single-cell based metagenome sequencing. This effort has yielded the most extensive collection of bacteria linked to unicellular protists to date. From this dataset, we identified 883 bacterial species capable of cohabiting with ciliates, unveiling the genomes of 116 novel bacterial cohabitants along with 7 novel archaeal cohabitants. Highlighting the intimate relationship between ciliates and their cohabitants, our study unveiled that over 90% of ciliates coexist with bacteria, with individual hosts fostering symbiotic relationships with multiple bacteria concurrently, resulting in the observation of seven distinct symbiotic patterns among bacteria. Our exploration of symbiotic mechanisms revealed the impact of host digestion on the intracellular diversity of cohabitants. Additionally, we identified the presence of eukaryotic-like proteins in bacteria as a potential contributing factor to their resistance against host digestion, thereby expanding their potential host range. CONCLUSIONS: As the first large-scale analysis of prokaryotic associations with ciliate protists, this study provides a valuable resource for future research on eukaryotic-bacterial symbioses. Video Abstract.

Spatiotemporal patterns of the pregnancy microbiome and links to reproductive disorders.

The microbiome of females undergoes extensive remodeling during pregnancy, which is likely to have an impact on the health of both mothers and offspring. Nevertheless, large-scale integrated investigations characterizing microbiome dynamics across key body habitats are lacking. Here, we performed an extensive meta-analysis that compiles and analyzes microbiome profiles from  >10,000 samples across the gut, vagina, and oral cavity of pregnant women from diverse geographical regions. We have unveiled unexpected variations in the taxonomic, functional, and ecological characteristics of microbial communities throughout the course of pregnancy. The gut microbiota showed distinct trajectories between Western and non-Western populations. The vagina microbiota exhibited fluctuating transitions at the genus level across gestation, while the oral microbiota remained relatively stable. We also identified distinctive microbial signatures associated with prevalent pregnancy-related disorders, including opposite variations in the oral and gut microbiota of patients with gestational diabetes and disrupted microbial networks in preterm birth. This study establishes a comprehensive atlas of the pregnancy microbiome by integrating multidimensional datasets and offers foundational insights into the intricate interplay between microbes and host factors that underlie reproductive health.

Micro and nano plastics release from a single absorbable suture into simulated body fluid.

Synthetic polymers are widely used in medical devices and implants where biocompatibility and mechanical strength are key enablers of emerging technologies. One concern that has not been widely studied is the potential of their microplastics (MPs) release. Here we studied the levels of MP debris released following 8-week in vitro tests on three typical polyglycolic acid (PGA) based absorbable sutures (PGA 100, PGA 90 and PGA 75) and two nonabsorbable sutures (polypropylene-PP and polyamide-PA) in simulated body fluid. The MP release levels ranked from PGA 100 > > PGA 90 > PGA 75 > > PP ∼ PA. A typical PGA 100 suture released 0.63 ± 0.087 million micro (MPs > 1 µm) and 1.96 ± 0.04 million nano (NPs, 200-1000 nm) plastic particles per centimeter. In contrast, no MPs were released from the nonabsorbable sutures under the same conditions. PGA that was co-blended with 10-25% L-lactide or epsilon-caprolactone resulted in a two orders of magnitude lower level of MP release. These results underscore the need to assess the release of nano- and microplastics from medical polymers while applied in the human body and to evaluate possible risks to human health.

MAMI: a comprehensive database of mother-infant microbiome and probiotic resources.

Extensive evidence has demonstrated that the human microbiome and probiotics confer great impacts on human health, particularly during critical developmental stages such as pregnancy and infancy when microbial communities undergo remarkable changes and maturation. However, a major challenge in understanding the microbial community structure and interactions between mothers and infants lies in the current lack of comprehensive microbiome databases specifically focused on maternal and infant health. To address this gap, we have developed an extensive database called MAMI (Microbiome Atlas of Mothers and Infants) that archives data on the maternal and neonatal microbiome, as well as abundant resources on edible probiotic strains. By leveraging this resource, we can gain profound insights into the dynamics of microbial communities, contributing to lifelong wellness for both mothers and infants through precise modulation of the developing microbiota. The functionalities incorporated into MAMI provide a unique perspective on the study of the mother-infant microbiome, which not only advance microbiome-based scientific research but also enhance clinical practice. MAMI is publicly available at https://bioinfo.biols.ac.cn/mami/.

Machine learning-assisted assessment of key meteorological and crop factors affecting historical mulch pollution in China.

Degraded mulch pollution is of a great concern for agricultural soils. Although numerous studies have examined this issue from an environmental perspective, there is a lack of research focusing on crop-specific factors such as crop type. This study aimed to explore the correlation between meteorological and crop factors and mulch contamination. The first step was to estimate the amounts of mulch-derived microplastics (MPs) and phthalic acid esters (PAEs) during the rapid expansion period (1993-2012) of mulch usage in China. Subsequently, the Elastic Net (EN) and Random Forest (RF) models were employed to process a dataset that included meteorological, crop, and estimation data. At the national level, the RF model suggested that coldness in fall was crucial for MPs generation, while vegetables acted as a key factor for PAEs release. On a regional scale, the EN results showed that crops like vegetables, cotton, and peanuts remained significantly involved in PAEs contamination. As for MPs generation, coldness prevailed over all regions. Aridity became more critical for southern regions compared to northern regions due to solar radiation. Lastly, each region possessed specific crop types that could potentially influence its MPs contamination levels and provide guidance for developing sustainable ways to manage mulch contamination.

Role of suspended solids on the co-precipitation of pathogenic indicators and antibiotic resistance genes with struvite from digested swine wastewater.

Struvite recovered from wastewater contains high concentration of fecal indicator bacteria (FIB), porcine adenoviruses (PAdV) and antibiotic resistance genes (ARGs), becoming potential resources of these microbial hazards. Understanding the precipitation behavior of pathogenic indicators and ARGs with suspended solids (SS) will provide the possible strategy for the control of co-precipitation. In this study, SS was divided into high-density SS (separated by centrifugation) and low-density SS (further separated by filtration), and the role of SS on the co-precipitation of FIB, PAdV and ARGs was investigated. The distribution analysis showed that 35.5-73.0% FIB, 79.6% PAdV and 64.5-94.8% ARGs existed in high-density SS, while the corresponding values were 26.9-64.4%, 11.7% and 3.5-24.3% in low-density SS. During struvite generation, 82.7-96.9% FIB, 75.5% PAdV and 56.3-86.5% ARGs were co-precipitated into struvite. High-density SS contributed 20.7-68.5% FIB, 63.9% PAdV and 38.7-87.2% ARGs co-precipitation, and the corresponding contribution of low-density SS was 31.4-79.2%, 3.9% and 6.2-54.7%. Moreover, the precipitated SS in struvite obviously decreased inactivation efficiency of FIB and ARGs in drying process. These results provide a potential way to control the co-precipitation and inactivation of FIB, PAdV and ARGs in struvite through removing high-density SS prior to struvite recovery.

Co-precipitation of heavy metals with struvite from digested swine wastewater: Role of suspended solids.

Struvite production can recover ammonia and phosphorous from digested wastewater as fertilizer. During struvite generation, most of the heavy metals was co-precipitated with ammonia and phosphorous into struvite. Understanding the precipitation behavior of heavy metals with suspended solids (SS) might provide the possible strategy for the control of co-precipitation. In this study, the distribution of heavy metals in SS and their role on the co-precipitation during struvite recovery from digested swine wastewater were investigated. The results showed that the concentration of heavy metal (including Mn, Zn, Cu, Ni, Cr, Pb and As) ranged from 0.05 to 17.05 mg/L in the digested swine wastewater. The distribution analysis showed that SS with particles > 50 µm harbored most of individual heavy metal (41.3-55.6%), followed by particles 0.45-50 µm (20.9-43.3%), and SS-removed filtrate (5.2-32.9%). During struvite generation, 56.9-80.3% of individual heavy metal was co-precipitated into struvite. The contributions of SS with particles > 50 µm, 0.45-50 µm, and SS-removed filtrate on the individual heavy metal co-precipitation were 40.9-64.3%, 25.3-48.3% and 1.9-22.9%, respectively. These finding provides potential way for controlling the co-precipitation of heavy metals in struvite.

TGase-induced Cd tolerance by boosting polyamine, nitric oxide, cell wall composition and phytochelatin synthesis in tomato.

In highly intensive greenhouse vegetable production, soil acidification was caused by excessive fertilization, increasing cadmium (Cd) concentrations in the vegetables, which bears environmental hazards and is a negative influence on vegetables and humans. Transglutaminases (TGases), a central mediator for certain physiological effects of polyamines (PAs) in the plant kingdom, play important roles in plant development and stress response. Despite increased research on the crucial role of TGase in protecting against environmental stresses, relatively little is known about the mechanisms of Cd tolerance. In this study, we found, TGase activity and transcript level, which was upregulated by Cd, and TGase-induced Cd tolerance related to endogenous bound PAs increase and formation of nitric oxide (NO). Plant growth of tgase mutants was hypersensitive to Cd, chemical complementation by putrescine, sodium nitroprusside (SNP, nitric oxide donor) or gain of function TGase experiments restore Cd tolerance. α-diflouromethylornithine (DFMO, a selective ODC inhibitor) and 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO, NO scavenger), were respectively found declined drastically endogenous bound PA and NO content in TGase overexpression plants. Likewise, we reported that TGase interacted with polyamine uptake protein 3 (Put3), and the silencing of Put3 largely reduced TGase-induced Cd tolerance and bound PAs formation. This salvage strategy depends on TGase-regulated synthesis of bound PAs and NO that is able to positively increase the concentration of thiol and phytochelatins, elevate Cd in the cell wall, as well as induce the levels of expression Cd uptake and transport genes. Collectively, these findings indicate that TGase-mediated enhanced levels of bound PA and NO acts as a vital mechanism to protect the plant from Cd-caused toxicity.

Application of 3D Printing Technology in Sensor Development for Water Quality Monitoring.

The development of sensors for water quality monitoring is crucial to protect water quality, aquatic biota and human health. Traditional sensor manufacturing methods have significant drawbacks, such as low fabrication freedom, limited material choice and expensive manufacturing cost. As a possible alternative method, 3D printing technologies are increasingly popular in sensor development due to their high versatility, fast fabrication/modification, powerful processing of different materials and ease of incorporation with other sensor systems. Surprisingly, a systematic review examining the application of 3D printing technology in water monitoring sensors has not yet been conducted. Here, we summarized the development history, market share and advantages/disadvantages of typical 3D printing techniques. Specifically focused on the 3D-printed sensor for water quality monitoring, we then reviewed the applications of 3D printing in the development of sensors' supporting platform, cell, sensing electrode as well as all-3D-printed sensors. The fabrication materials and processing, and the sensor's performances regarding detected parameters, response time and detection limit/sensitivity, were also compared and analyzed. Finally, the current drawbacks of 3D-printed water sensors and potential directions for future study were discussed. This review will substantially promote the understanding of 3D printing technology used in water sensor development and benefit the protection of water resources.

The efficiency of quick response code versus telephone contact for post-discharge follow-up after ophthalmic day surgery: a randomized controlled trial.

PURPOSE: To assess and compare the efficiency of quick response (QR) code versus telephone contact for post-discharge follow-up in patients receiving low-risk ophthalmic day surgery. METHODS: One hundred and sixty patients undergoing strabismus day-care surgery with general anesthesia were randomly allocated to either the intervention group using QR code (QR group) or the control group receiving telephone call (TEL group) for post-discharge follow-up. The primary outcome was the follow-up overall attendance rate on the second postoperative day. Secondary outcomes included attendance rate at the first scheduled follow-up, number of text message reminders, elapsed time and estimated cost for follow-up, omission rate of follow-up responses, and patient satisfaction. RESULTS: The overall attendance rate of follow-up was significantly higher in the QR group than that in the TEL group (97.5% vs. 87.5%, p = 0.016). As compared with the TEL group, the QR group significantly reduced the number of text message reminders with higher attendances at the first scheduled follow-up (p < 0.001, p = 0.001). Besides, the TEL group cost a median time of 258 s and a median cost of RMB 5.8 yuan to complete a follow-up consultant, but was associated with a significantly high omission rate of follow-up responses comparing to the QR group (p = 0.002). Patient satisfaction was comparable between two groups. CONCLUSION: QR code follow-up can be more efficient than traditional telephone contact in assessing the post-discharge recovery after strabismus day surgery, which provides a safe and intuitively alternative follow-up pathway for identifying issues that may necessitate further clinical care for more low-risk ophthalmic day surgeries.

Recent Implementations of Hydrogel-Based Microbial Electrochemical Technologies (METs) in Sensing Applications.

Hydrogel materials have been used extensively in microbial electrochemical technology (MET) and sensor development due to their high biocompatibility and low toxicity. With an increasing demand for sensors across different sectors, it is crucial to understand the current state within the sectors of hydrogel METs and sensors. Surprisingly, a systematic review examining the application of hydrogel-based METs to sensor technologies has not yet been conducted. This review aimed to identify the current research progress surrounding the incorporation of hydrogels within METs and sensors development, with a specific focus on microbial fuel cells (MFCs) and microbial electrolysis cells (MECs). The manufacturing process/cost, operational performance, analysis accuracy and stability of typical hydrogel materials in METs and sensors were summarised and analysed. The current challenges facing the technology as well as potential direction for future research were also discussed. This review will substantially promote the understanding of hydrogel materials used in METs and benefit the development of electrochemical biosensors using hydrogel-based METs.

Structure evolution of air cathodes and their application in electrochemical sensor development and wastewater treatment.

Cathode structure and material are the most important factors to determine the performance and cost of single chamber air-cathode microbial fuel cell (MFC), which is the most promising type of MFC technology. Since the first air cathode was invented in 2004, five major structures (1-layer, 2-layer, 3-layer, 4-layer and separator-support) have been invented and modified to fit new material, improve power performance and lower MFC cost. This paper reviewed the structure evolution of air cathodes in past 18 years. The benefits and drawbacks of these structures, in terms of power generation, material cost, fabrication procedure and modification process are analyzed. The practical application cases (e.g., sensor development and wastewater treatment) employed with different cathode structures were also summarized and analyzed. Based on practical performance and long-term cost analysis, the 2-layer cathode demonstrated much greater potential over other structures. Compared with traditional activated-sludge technology, the cost of an MFC-based system is becoming competitive when employing with 2-layer structure. This review not only provides a detailed development history of air cathode but also reveals the advantages/disadvantages of air cathode with different structures, which will promote the research and application of air-cathode MFC technology.

Microbial transmission, colonisation and succession: from pregnancy to infancy.

The microbiome has been proven to be associated with many diseases and has been used as a biomarker and target in disease prevention and intervention. Currently, the vital role of the microbiome in pregnant women and newborns is increasingly emphasised. In this review, we discuss the interplay of the microbiome and the corresponding immune mechanism between mothers and their offspring during the perinatal period. We aim to present a comprehensive picture of microbial transmission and potential immune imprinting before and after delivery. In addition, we discuss the possibility of in utero microbial colonisation during pregnancy, which has been highly debated in recent studies, and highlight the importance of the microbiome in infant development during the first 3 years of life. This holistic view of the role of the microbial interplay between mothers and infants will refine our current understanding of pregnancy complications as well as diseases in early life and will greatly facilitate the microbiome-based prenatal diagnosis and treatment of mother-infant-related diseases.

Alcohol Pretreatment to Eliminate the Interference of Micro Additive Particles in the Identification of Microplastics Using Raman Spectroscopy.

Raman spectroscopy is an indispensable tool in the analysis of microplastics smaller than 20 µm. However, due to its limitation, Raman spectroscopy may be incapable of effectively distinguishing microplastics from micro additive particles. To validate this hypothesis, we characterized and compared the Raman spectra of six typical slip additives with polyethylene and found that their hit quality index values (0.93-0.96) are much higher than the accepted threshold value (0.70) used to identify microplastics. To prevent this interference, a new protocol involving an alcohol treatment step was introduced to successfully eliminate additive particles and accurately identify microplastics. Tests using the new protocol showed that three typical plastic products (polyethylene pellets, polyethylene bottle caps, and polypropylene food containers) can simultaneously release microplastic-like additive particles and microplastics regardless of the plastic type, daily-use scenario, or service duration. Micro additive particles can also adsorb onto and modify the surfaces of microplastics in a manner that may potentially increase their health risks. This study not only reveals the hidden problem associated with the substantial interference of additive particles in microplastic detection but also provides a cost-effective method to eliminate this interference and a rigorous basis to quantify the risks associated with microplastic exposure.

Microbe-Based Sensor for Long-Term Detection of Urine Glucose.

The development of a reusable and low-cost urine glucose sensor can benefit the screening and control of diabetes mellitus. This study focused on the feasibility of employing microbial fuel cells (MFC) as a selective glucose sensor for continuous monitoring of glucose levels in human urine. Using MFC technology, a novel cylinder sensor (CS) was developed. It had a quick response time (100 s), a large detection range (0.3-5 mM), and excellent accuracy. More importantly, the CS could last for up to 5 months. The selectivity of the CS was validated by both synthetic and actual diabetes-negative urine samples. It was found that the CS's selectivity could be significantly enhanced by adjusting the concentration of the culture's organic matter. The CS results were comparable to those of a commercial glucose meter (recovery ranged from 93.6% to 127.9%) when the diabetes-positive urine samples were tested. Due to the multiple advantages of high stability, low cost, and high sensitivity over urine test strips, the CS provides a novel and reliable approach for continuous monitoring of urine glucose, which will benefit diabetes assessment and control.

Unfavourable intrauterine environment contributes to abnormal gut microbiome and metabolome in twins.

OBJECTIVE: Fetal growth restriction (FGR) is a devastating pregnancy complication that increases the risk of perinatal mortality and morbidity. This study aims to determine the combined and relative effects of genetic and intrauterine environments on neonatal microbial communities and to explore selective FGR-induced gut microbiota disruption, metabolic profile disturbances and possible outcomes. DESIGN: We profiled and compared the gut microbial colonisation of 150 pairs of twin neonates who were classified into four groups based on their chorionicity and discordance of fetal birth weight. Gut microbiota dysbiosis and faecal metabolic alterations were determined by 16S ribosomal RNA and metagenomic sequencing and metabolomics, and the long-term effects were explored by surveys of physical and neurocognitive development conducted after 2~3 years of follow-up. RESULTS: Adverse intrauterine environmental factors related to selective FGR dominate genetics in their effects of elevating bacterial diversity and altering the composition of early-life gut microbiota, and this effect is positively related to the severity of selective FGR in twins. The influence of genetic factors on gut microbes diminishes in the context of selective FGR. Gut microbiota dysbiosis in twin neonates with selective FGR and faecal metabolic alterations features decreased abundances of Enterococcus and Acinetobacter and downregulated methionine and cysteine levels. Correlation analysis indicates that the faecal cysteine level in early life is positively correlated with the physical and neurocognitive development of infants. CONCLUSION: Dysbiotic microbiota profiles and pronounced metabolic alterations are associated with selective FGR affected by adverse intrauterine environments, emphasising the possible effects of dysbiosis on long-term neurobehavioural development.

The influence of drinking water constituents on the level of microplastic release from plastic kettles.

Microplastic (MP) release from household plastic products has become a global concern due to the high recorded levels of microplastic and the direct risk of human exposure. However, the most widely used MP measurement protocol, which involves the use of deionized (DI) water, fails to account for the ions and particles present in real drinking water. In this paper, the influence of typical ions (Ca2+/HCO3-, Fe3+, Cu2+) and particles (Fe2O3 particles) on MP release was systematically investigated by conducting a 100-day study using plastic kettles. Surprisingly, after 40 days, all ions resulted in a greater than 89.0% reduction in MP release while Fe2O3 particles showed no significant effect compared to the DI water control. The MP reduction efficiency ranking is Fe3+ ≈ Cu2+ > Ca2+/HCO3- > > Fe2O3 particles ≈ DI water. Physical and chemical characterization using SEM-EDX, AFM, XPS and Raman spectroscopy confirmed Ca2+/HCO3-, Cu2+ and Fe3+ ions are transformed into passivating films of CaCO3, CuO, and Fe2O3, respectively, which are barriers to MP release. In contrast, there was no film formed when the plastic was exposed to Fe2O3 particles. Studies also confirmed that films with different chemical compositions form naturally in kettles during real life due to the different ions present in local regional water supplies. All films identified in this study can substantially reduce the levels of MP release while withstanding the repeated adverse conditions associated with daily use. This study underscores the potential for regional variations in human MP exposure due to the substantial impact water constituents have on the formation of passivating film formation and the subsequent release of MPs.

Zero-valent iron mediated alleviation of methanogenesis inhibition induced by organoarsenic roxarsone.

Zero-valent iron (ZVI) can enhance anaerobic digestion, and has great potential to alleviate/eliminate methanogenesis inhibition. Little is known about the feasibility of utilizing ZVI to alleviate methanogenesis inhibition that is caused by typical animal feed additive roxarsone in livestock wastewater. In this study, the role of ZVI on alleviating roxarsone-induced methanogenic inhibition and its mechanisms were investigated. With the increase of roxarsone concentration from 5 to 50 mg/L, the inhibition of methanogenesis increased from 3.0% to 65.7%. This inhibition was alleviated by 80.7% and 57.2% when 1.0 and 10.0 g/L ZVI were added, respectively. Due to ZVI addition, an efficient arsenic immobilization onto ZVI (45.4-85.8%) was achieved mainly through the formation of FeAsO4 precipitate and adsorption by ZVI. Under the function of ZVI, hydrogenotrophic methanogenic activity was obviously restored. The microbial community analysis indicates that the ZVI-regulated alleviation on the methanogenesis inhibition was attributed to the enrichment of Methanobacterium and Methanosarcina. The findings from this study demonstrate that ZVI addition is an effective way for treatment of organoarsenic-contaminated wastewater.